Field of the Invention
The invention relates in general to the field of semiconductors, and specifically to a semiconductor memory configuration having selection transistors and storage capacitors constructed with at least one multi-layered electrode.
Such integrated semiconductor memory configurations are described in European Patent Application EP 0 514 149A1, where the upper and lower electrodes which bound a dielectric layer at the top and bottom are configured in a multilayered manner. The layer facing the substrate more closely has a high melting point and does not react with the dielectric layer. Titanium, tantalum, tungsten, molybdenum and the like are examples of materials that can be used for the layer facing the substrate more closely. Platinum, palladium, rhodium and aluminum are examples of materials that can be used for the layer configured above the former layer. The upper electrode seated on the dielectric layer consequently has, as shown by an example given in European Patent Application EP 0 514 149 (See FIG. 1 therein), a lower layer made from titanium and a layer made from platinum seated above the lower layer. The titanium layer is intended to have a thickness of between 10 and 150 nm and the platinum layer a thickness of between 100 and 1200 nm.
Oxide-ceramic dielectrics are being used for the storage capacitor since these dielectrics make it possible to realize comparatively large capacitances in conjunction with a small space requirement. High-.epsilon.materials such as, for example, (Ba.sub.x Sr.sub.1-x TiO.sub.3) or the ferroelectric material SrBi.sub.2 Ta.sub.2 O.sub.9 are used as oxide-ceramic dielectrics. Because of the high proportion of oxygen in the dielectric and the oxygen atmosphere that is needed during the deposition or during the heat treatment, electrode materials employed heretofore, such as aluminum, polysilicon or suicides, can no longer be used.
Therefore, platinum is being used as a new electrode material, as shown by U.S. Pat. No. 5,330,931 and U.S. Pat. No. 5,466,629, for example.
A satisfactory solution to the patterning of platinum has not been found heretofore. The etching operation is primarily carried out by physical processes using high-energy ions. Furthermore, it has become known to etch platinum anisotropically. However, the etching profiles that can be achieved are still not satisfactory in the case of anisotropic etching. Moreover, platinum has a higher electrical resistivity than, for example, aluminum, namely approximately 10 .mu.ohms*cm. These disadvantages have made platinum unattractive heretofore as an electrode material even though it has outstanding properties with regard to the junction with ferroelectrics and high-.epsilon. dielectrics.